Radio frequency (RF) circuits are widely used in a variety of applications, including communication systems, radio and television broadcasting, radar, and the like. In addition, many circuit blocks, such as receivers, transmitters, modulators, filters, transmission lines, oscillators, frequency synthesizers, and low-noise amplifiers, extensively use RF integrated circuits.
The use of RF integrated circuits, however, is not without problems. For example, the performance and the production yield for an RF integrated circuit are negatively affected by the variation in for the transistor device across temperature, the DC supply voltage, and manufacturing process variation.
To overcome these potential problems, conventional design schemes rely on voltage—and temperature-sensing circuits that adjust the bias points of the RF devices. However, a significant disadvantage with these design schemes is the reliance on empirical relationships between RF performance and temperature and between RF performance and supply voltage. Due to the inexact nature of these relationships, substantial chip-to-chip variation in RF performance results from the use of these conventional design schemes. Compensation for this variation is typically accomplished by increasing the performance margin of the entire system, which also substantially increases the cost of the system.